Limestone of the Mystic structural complex

Unit symbol: Dls
Age range Devonian (419.2 to 358.9 Ma)
Lithology: Sedimentary
Group name: Sedimentary rocks of the Mystic structural complex
Chiefly algal-laminated limestone and dolostone of shallow-marine origin. In eastern McGrath quadrangle, includes two members of the informal Saint Johns Hill formation of Bundtzen and others (1997a): Dls, which consists of brown to terra-cotta, micaceous, slightly pyritic, thinly laminated limestone, mudstone, siltstone, and lithic sandstone; and uDl, which consists of medium-gray, massive- to thick-bedded, micritic limestone that contains crypto-algal laminations, thin, black chert partings, and dolomitic nodules. Also includes two members of the informal Sheep Creek formation of Bundtzen and others (1997a): lDl, which consists of massive, thick-bedded, medium-gray limestone, rich in algal laminations and Amiphipora sp.; and lDd, which consists of light gray, dolomitized, algal(?) limestone. In the western McGrath and western Lime Hills quadrangles, includes unit uDl of Bundtzen (T.K. Bundtzen, Pacific Rim Geologic Consultants, written commun., 1997, 1998). In the Talkeetna quadrangle, Reed and Nelson (1980) describe thin-bedded gray micrite grading upward into fossiliferous, massive to reefoid biostromal beds of colonial rugose corals and massive stromatoporoids, which contain shelly faunas of late Middle and early Late Devonian age and locally faunas of late Early or Middle Devonian age. The stromatoporoid beds are overlain by dark-brown to black shales and thin limestone interbeds in the shale that contain conodonts of Late Devonian (upper half of Frasnian) age

Source map information

Source map Bundtzen, T.K., 1997, Written commun.
Symbol mDl
Unit name Cheeneetnuk Limestone
Description Cheeneetnuk limestone (Farewell Composite Terrane; Mystic Subterrane)
Lithology Sedimentary

Correlated geologic units

Label DSml
Description Carbonate rocks of the lower part of the Mystic stratigraphic sequence (Devonian and Silurian)
Geologic age Devonian
Geologic setting Sedimentary, carbonate
Lithology Form Importance
Limestone < Carbonate < Sedimentary Bed Major
Limestone < Carbonate < Sedimentary Bed Major
Marble < Metacarbonate < Metasedimentary < Metamorphic Greenschist Indeterminate, major
Mudstone < Clastic < Sedimentary Bed Indeterminate, major
Sandstone < Clastic < Sedimentary Bed Indeterminate, major
Siltstone < Clastic < Sedimentary Bed Indeterminate, major